I fly sparge. For a 10 gallon batch, I usually bring 8 gallons to 170 degrees and sparge until I reach 1.007 and stop. Most of the brew pub guys I've talked to stop their runnings at 1.007 so right or wrong, that''s what I've been doing.
So far I haven't had to use all the 8 gallons in my HLT. This is where the calibrated sight glass in the boil kettle helps to make sure I only boil until the volume is to where I need it to be to fit the wort into the primary's after cooling.
I've only been using Pro-mash for a few brew sessions and have been trying to fine tune my brewhouse numbers.